The interaction of fibronectin (fn) with native, polymeric collagen (collagen fibres): comparison with von Willebrand factor (vWf)-binding by collagen.

The binding of fn to collagen (type I) fibres has been found to resemble that of vWf in the following respects: Binding is rapid, specific, saturable, similar at 4 and 37 degrees C, and reduced by increasing ionic strength. Binding is not inhibited by native, monomeric collagen, suggesting a multivalent mechanism of interaction. Binding of fn occurs to a variety of collagen fragments (after their renaturation and polymerization), including, for example, the collagenase-derived TCA and TCB 3/4 and 1/4 molecular fragments and the peptides alpha 1(I)CB3, 6b, 7 and 8 obtained by cleavage with cyanogen bromide (CB), suggesting a wide distribution of binding sites on the native collagen molecule. As judged by the effect of heat-treatment, the native conformation of fn is required. Chemical modification indicates the involvement of arginyl residues in collagen and carboxyl groups in fn. However, fn and vWf did not compete with one another in binding to collagen, suggesting the participation of different collagen arginyl residues in the two interactions. Fn-binding differed from that of vWf in that the former was inhibited by denatured monomeric collagen (gelatin). Fn-binding was also inhibited by the fragment TCA in denatured form. The inhibitory activity was lost after chemical modification of arginyl residues in gelatin. Our results suggest that fn binding to collagen fibres and gelatin involves the same widely-distributed spectrum of binding sites.